One of the major problems facing developers of fluorescence imaging systems is accounting for intrinsic variations in a tissue's optical properties, such as its absorption and scattering, which attenuate and distort the emitted fluorescence. Without an accurate way to correct for these variations, the measurements made by today's commercial intraoperative visual fluorescence imaging (vFI) systems are qualitative, and therefore, purely subjective.

In what is viewed as a crucial step towards making fluorescence imaging a quantitative science, researchers in the US and Canada have unveiled a quantitative fluorescence imaging (qFI) approach that provides the absolute fluorophore concentration on a pixel-by-pixel basis across a wide field-of-view. The system runs in near real-time and has to date provided quantitative wide-field estimates of protoporphyrin IX (PpIX) concentrations in both rodent and human gliomas (Scientific Reports 2 798).

"Our qFI system integrates seamlessly into commercial surgical instrumentation and is also financially accessible," explained Pablo Valdés, from Dartmouth's Thayer School of Engineering and Geisel School of Medicine at Dartmouth. "We have used it in 12 human glioma cases to date, and our project's principle investigator David Roberts, chief neurosurgeon at Dartmouth, continues to move forward with its use."

Improving the practicality

This latest work builds on the team's development of a handheld probe that provided point-based assessments of fluorophore concentrations in tissue. Although promising results were achieved with this probe, development work continued to produce a wide-field system that was ultimately more practical and amenable to the surgical workflow.